None.
The invention relates generally to tamper indicating adhesive devices, and more particularly to devices such as tapes, labels, and label stock that indicate tampering attempts through internal delamination.
It is known to provide a tamper indicating device which may be adhered to various articles. Devices are known that indicate tampering by changing their appearance upon attempts to remove the device from the article.
These devices may provide some type of information, such as a serial number or other identification, or may provide an indication of the authenticity of the article. In such a case, it is desirable to provide an indication of tampering to prevent the device with the information thereon from being removed and re-adhered to another article.
Additionally, these devices may be placed on an article that is some type of container. In such a case, the tamper indicating device may be placed across two separable portions of the article to indicate if tampering has occurred to the contents of the container. For example, it may be desirable to adhere the tamper indicating device both to the flap and the main body of a card, envelope or carton. In this way, removal of the tamper indicating device to gain access to the contents will cause the device to provide an indication of tampering.
One particular tamper indication device is a film which utilizes a mixture of incompatible polymers such that when an attempt is made to remove the film (e.g., in the form of adhesive tape) from a substrate (such as a sealed package) the film internally xe2x80x9cdelaminates,xe2x80x9d causing the two polymers in the film to separate and split apart. This type of film can be known as Tamper Evident Delaminating (TED) film. One such film is described in U.S. Pat. No. 4,876,123 (""123), assigned to the assignee of the present application. In the ""123 patent, a light transmissive film is disclosed which is derived from a composition comprising 50 to 85 parts by weight of a first copolymer comprising at least one moiety derived from at least one olefinic monomeric unit and 50 to 15 parts by weight of a second copolymer comprising at least one moiety derived from at least one vinyl alcohol monomeric unit. The second copolymer is sufficiently incompatible to the first copolymers such that two phases are formed within the film, one of the phases being continuous. The film can be made into a tape which can include various colorants and indicia (e.g., printed lettering or flood coating) that provide an indication of tampering, as well as including an adhesive layer for adhering the film to an article. When the film delaminates, such as upon attempts to remove it from a container, it becomes more opaque so that the first indicia are obscured when viewed through the delaminated film, and the second indicia become perceptible over the delaminated opaque film. The ""123 patent explains that the film may be produced by any suitable film generating process, but is preferably produced by dry blending the first and second polymers together, air drying the blend at 200xc2x0 F. (93.3xc2x0 C.) for 48 hours, then extruding the blend onto a driven chilled roll.
U.S. Pat. No. 4,980,222 (""222) also assigned to the assignee of the present application discloses tamper indicating tape based on the same film as that disclosed in the ""123 patent. The devices disclosed in the ""222 patent include a variety of arrangements for obscuring and revealing tamper indicating messages and ways for adhering the tape to articles and is incorporated in its entirety herein.
An issue with TED film is that since TED film is designed to be very sensitive (in order to indicate when tampering has occurred) unintended pre-destruction (or pre-destruct) of the TED film may occur. For some constructions of TED film, pre-destruct occurs when forces caused by unwinding the adhesive coated TED film (or TED tape) from a roll or removing a release liner from an adhesive on the TED film cause the TED film to begin to delaminate. Pre-destruct may occur with some constructions of TED films even with premium release systems (i.e., liner release values as low as 10 grams/inch (3.9 grams/cm)) such as is available from DCP-Lojha, Dixon, Ill. If indicia are included on the TED film, the pre-destruct causes the covert message to appear and gives a xe2x80x9cfalse positivexe2x80x9d tampering signal (or in other words, a false indication that tampering has occurred). The TED film may completely delaminate due to these pre-destruct forces, or may delaminate at discrete portions of the film, also known as xe2x80x9cfracturing.xe2x80x9d
The invention is a tamper indicating device including a backing. The backing includes a first phase and a second phase. The backing is normally light transmissive, but a peeling force can cause the backing to internally delaminate and become more opaque. A first skin layer is fixed to the backing which minimizes pre-destruct of the backing. A layer of adhesive is applied to the first skin layer, which can be affixed to a substrate.
The invention is also a method for forming a tamper indicating device. A blown film backing and a skin layer are co-extruded. The backing includes a first phase and a second phase. The backing is normally light transmissive and becomes more opaque upon internal delamination. A pressure sensitive adhesive is applied to the skin layer opposite the backing.